Inherent in the plants of various branches of industry wherein it is practically impossible to eliminate the escape of toxic gases into enclosed working spaces and surrounding atmosphere from the plant machinery lacking complete gas-tightness is a problem of sanitary purification of the centralized gas flows through separating toxic gaseous constituents therefrom. Problems like this one can be solved by improved working conditions for the employees, prevention of corrosion of the special-purpose equipment, particularly the costly electronic flow-process control devices, and reduction of the environmental pollution. These problems tend to become more acute with time due to a general increase in the industrial production, more rigid sanitary regulations for industrial gas wastes and for toxic constituents in enclosed spaces of plants. Since it is impossible to find a drastic approach to the problem of ensuring absolute gas-tightness of the equipment or complete automation of the technological processes, a most practicable way of extracting toxic constituent from the ambient air is the purification of the centralized gas flows by means of various equipment arrangements and flow diagrams, enabling the reduction to a certain degree of the level of the gas stream contamination by toxic constituents and to subsequently utilize the substances withdrawn therefrom. The known constructions of filters for separating toxic constituents from gases generally contain the same feature, namely, a removable filtering elements (such as cellular, cartridge, sleeve, foldable, frame and bag filtering elements) adapted to adsorb the toxic constituents to be thereafter extracted from the body of the filter and regenerated in a separate unit. Regeneration is effected by chemisorbtion of the toxic constituents or by replacing used elements by fresh non-regenerable sorbents. Special supports and seals for filtering elements intended to increase gas-tightness and structural rigidity of apparatus make replacement of the elements a labour-consuming operation which, in turn, leads to limited application of such filters for gas purification.
Known in the art is an apparatus for continuous removal of gases (cf. U.S. Pat. No. 3,498,026, Cl. 55-73, published 1970) comprising a housing having inlet and outlet openings for the passage of ambient air. The housing is partitioned into upper and lower chambers. The lower chamber located below the air inlet opening contains a self-sustaining liquid tank unit. Accommodated essentially vertically relative to the housing and inside thereof is a wide movable endless belt, i.e. the filtering element, fabricated from a fibrous chemisorbing material capable of adsorbing unwanted constituents of the ambient air flow, said belt being suspended and guided by a plurality of rollers mounted within the housing on the top and bottom walls thereof. A section of the belt in the upper chamber screens the air inlet providing thereby the removal of unwanted gases. In the lower chamber saturated with unwanted gases a section of the fibrous chemisorbing belt passes through the liquid tank (e.g., hot water) wherein removal of the adsorbed substances and regeneration of the belt material takes place.
The heretofore described apparatus features inefficient utilization of the interior space by chemisorbing material because the filtering element proper is a single chemisorbing belt acting to screen a narrow cross-sectional portion of the apparatus. This substantially reduces specific adsorption of the toxic gases relative to the per unit volume of the apparatus. Also, the apparatus features low ratio between the volume of the chemisorbing material proper and the volume of the regenerating liquid, since in the course of operation the moving chemisorbing belt must be completely immersed into the regenerating liquid tank with sufficient dwell time for contact between the belt and the liquid. This results in an increased specific consumption of the regenerating liquid and low concentration of contaminating substances released thereinto after said liquid leaves the regenerating chamber, which complicates subsequent utilization thereof.
In addition, it is difficult to achieve gas-tightness in various portions of the apparatus with a wide belt continuously moving between the upper and lower chambers, which have different operating conditions.
Also known is an ionic filter for separating agressive substances from gases (cf. USSR Inventor's Certificate No. 507,334, Cl. B 01 d 23/04, published 1976) comprising a housing having openings for inlet of contaminated gas and discharge of the purified gas arranged essentially on the side walls thereof. Rigidly secured inside the housing is a stationary filtering element in the form of a sleeve fabricated from an ion-exchangable fibrous material and mounted with the open end thereof on the inlet opening for the contaminated gas. Arranged at the bottom of the housing is a liquid tank, the liquid acting to regenerate the filtering element. A closed end of the sleeve is secured to the bottom of the tank. In the course of gas purification in the filter, said tank contains no liquid acting to regenerate the filtering element and under combined action of the weight of the tank and a float the ion-exchangable fibrous sleeve remains in a stretched state. Upon saturation of the ion-exchangable fibrous material with toxic gases, the gas inlet opening is closed by a gate so as to prevent the flow of gas through the filter. Thereafter, a regenerating liquid is fed into the lower portion of the housing until the tank and the float are raised to a selected height whereat the sleeve is completely immersed into the regenerating liquid. After a certain dwell time the liquid is drained out of the tank and the filter is ready for further purification.
Owing to the fact that the filtering element is in the form of a sleeve completely immersible into the regenerating liquid, said filter features low fillability of the filter volume with the chemisorbing material resulting in a reduced specific adsorption of the toxic gases per unit volume of the filter and in an increased specific consumption of the regenerating liquid during a single cycle. Furthermore, the operating mode of the heretofore described filter is inherently noncontinuous, requiring to completely discontinue the operation thereof for regeneration of the contaminated filtering element.